diff --git a/core/math/parser/parser-tests.factor b/core/math/parser/parser-tests.factor
index e885b23278..1705434f6b 100644
--- a/core/math/parser/parser-tests.factor
+++ b/core/math/parser/parser-tests.factor
@@ -5,6 +5,22 @@ IN: math.parser.tests
 [ f string>number ]
 unit-test
 
+[ f ]
+[ ";" string>number ]
+unit-test
+
+[ f ]
+[ "<>" string>number ]
+unit-test
+
+[ f ]
+[ "^" string>number ]
+unit-test
+
+[ f ]
+[ "789:;<=>?@" string>number ]
+unit-test
+
 [ f ]
 [ "12345abcdef" string>number ]
 unit-test
diff --git a/core/math/parser/parser.factor b/core/math/parser/parser.factor
index 18ccf132cc..ee022b64a4 100644
--- a/core/math/parser/parser.factor
+++ b/core/math/parser/parser.factor
@@ -5,11 +5,10 @@ IN: math.parser
 
 : digit> ( ch -- n )
     {
-        { [ dup CHAR: 9 <= ] [ CHAR: 0 - ] }
-        { [ dup CHAR: a <  ] [ CHAR: A 10 - - ] }
-        [ CHAR: a 10 - - ]
-    } cond
-    dup 0 < [ drop 255 ] when ; inline
+        { [ dup CHAR: 9 <= ] [ CHAR: 0 -      dup  0 < [ drop 255 ] when ] }
+        { [ dup CHAR: a <  ] [ CHAR: A 10 - - dup 10 < [ drop 255 ] when ] }
+                             [ CHAR: a 10 - - dup 10 < [ drop 255 ] when ]
+    } cond ; inline
 
 <PRIVATE